Iron Parts, Chain drive uses sprockets and a roller chain, which requires both lubrication and adjustment for elongation that occurs through wear. The lubricant is subject to being thrown off the fast-moving chain and results in grime and dirt build up. Chains do deteriorate, and excessive wear on the front and rear sprockets can be dangerous. In a chain drive the power is transmitted into the real wheel via a cush drive. Conventional roller chain drives suffer the potential for vibration, as the effective radius of action in a chain and sprocket combination constantly changes during revolution. If a drive sprocket rotates at constant RPM, then the chain must accelerate and decelerate constantly. Most chain-driven motorcycles are fitted with a rubber bushed rear wheel hub to eliminate this vibration issue.